Documentation: fix spelling in design-patterns

2. container_of()

~~~~~~~~~~~~~~~~~

Continuing on the above example we add a offloaded work:

Continuing on the above example we add an offloaded work:

struct foo {

    spinlock_t lock;

    (...)

}

The design pattern is the same for a a hrtimer or something similar that will

The design pattern is the same for an hrtimer or something similar that will

return a single argument which is a pointer to a struct member in the

callback.